Patent GB-981407-A (GB)
Title: Improvements in or relating to centrifuging apparatus
IPC: B04B5/04
Filed: 1961-09-27
Abstract: 981,407. Centrifugal separators. RESEARCH SPECIALTIES CO. Sept. 27, 1961 [Oct. 7, 1960], No. 34591/61. Headng B2P. [Also in Division B8] An automatic centrifuge for use preparatory to the chemical analysis of samples contained in tubes 23, Figs. 1, 2 and 4, for causing material of different densities to settle in the tubes comprises a conveyer 65 for supporting a number of tubes and presenting them in sequence to a station A, Fig. 2, adjacent to a centrifuging rotor 21, and a transfer device 25 for transporting tubes to be centrifuged from the station to the rotor and tubes which have been centrifuged from the rotor to the station. The conveyer 65 is in the form of ring-shaped turntable surrounding the rotor 21 which is provided around its periphery with a number of pivoted receptacles 24, each receiving on rubber buffers 28, Fig. 4, two sample tubes 23 and arranged to swing outwardly into horizontal position when the rotor is rotated. Each of a number of posts 67 provided around the turntable rotatably supports a spool 64 carrying twelve tubes 23 in a circular assembly. The turntable is indexed to bring each spool in turn to a position in which it is itself indexed to position successive pairs of tubes on the spool at the station A for interchange by the transfer device 25 with a pair of centrifuged tubes in one of the receptacles 24 on the rotor at a station B ; the rotor is itself indexed between successive operations of the transfer device to bring successive receptacles 24 to the station B. Centrifuging rotation of the rotor occurs after all the tubes on the spool have been exchanged with centrifuged tubes on the rotor, and the turntable is then indexed to bring the next spool to transfer position. The rotor 21 is disposed in a housing 34, 36, Fig. 4, supported on floating mountings 37, 38, 39 for damping out vibrations and is carried by a vertical shaft 31 which is driven for the centrifuging operations by a motor 35 through belting 35a, Fig. 1, and for the indexing of the rotor by the controlled operation of a reversible motor 42, Fig. 4, and gearing 44, 46 arranged to be rendered effective when the motor 35 is ineffective by the energization of an electromagnetic clutch 47, 48. The motor 42 is controlled by a peripherally-notched plate 54 fixed to the shaft 31 and arranged so to intercept light rays passing from sources 53 to corresponding sets of photoelectric cells 52a, 52b, in the control circuit of the motor that each indexing operation consists of fast drive by the motor to bring the next receptacle 24 up to and slightly past the station B, followed by reverse slow drive caused by the notch 55, Fig. 6, of the plate 54 then rendering the cell 52a effective, and stopping of the motor with a receptacle in correct position at the station when the portion 57 of the notch uncovers the cell 52b. Drive of the turntable 65 to bring successive spools 64 to transfer position and the stepped rotation of the spool at station A are effected from a motor 74, Fig. 7, through a sprocket 77, Fig. 2, engaging a chain 78 circularly arranged in engagement with sprockets 79 which are journalled on the posts 67 and have pin-andslot connections with the respective spools. The drive between the motor and sprocket 77 provides for intermittent rotation of the latter through 180 degrees by means of a pawl 108, Fig. 7, which is connected by a link 106 with a motor-driven gear 84 and coacts with a toothed disc 109 geared to the sprocket. The indexing movement of the chain 78 produced by each half revolution of the sprocket 77 results in either an index of the spools on their posts to the extent of one complete revolution less two tube spaces provided a latch 104, Fig. 2, then stops rotation of the turntable, or indexing of the turntable without relative indexing of the spools provided the latch is released. With a new spool at the transfer position, each of the first six indexing movements of the chain causes index of the spool to station A and is followed by an interchange operation of the transfer device. Centrifuging rotation of the rotor occurs during the next six movements of the chain, and at every twelfth movement of the chain the latch 104 is automatically released by linkage actuated by an arm 94, Fig. 7, driven from the motor-driven gear 84 so as to rotate the turntable one index space, after which the latch is again effective. Removal of the centrifuged tubes is carried out from the spool 64 which is one index step removed from the transfer position, alternate tubes being removed from the spool at the index station C as the spool is indexed. The transfer device 25 comprises a head 121, Fig. 1, which is carried by a rotatable and vertically-movable shaft 124 located midway between stations A and B and provided at each of its opposite ends with two sets of depending fingers 122 arranged to be swung about vertical axes into and out of gripping position under the rims of a pair of tubes 23. The shaft and fingers are automatically controlled in a cycle in which, assuming the head to be in a lowered position, all four sets of fingers are simultaneously actuated into gripping relation with the pairs of tubes to be interchanged, the head is raised, rotated through 180 degrees and lowered, and all the fingers are simultaneously withdrawn so as to deposit the tubes in interchanged positions on the spool and rotor. The drive of the shaft 124 to achieve this cycle is from a motor 141, Fig. 11, by chain gearing 126, Fig. 11, which is so arranged that, with the head held against rotation in all except its uppermost position by a vertical rod 149, Fig. 1, engaging one or other of two peripheral notches in the head, the shaft and head are reciprocated vertically, a limit switch 146, Fig. 11, being actuated by a pin 143 at each end of the stroke of the shaft to reverse the motor, and, with the head in the upper released position, the shaft and head are rotated through 180 degrees by gearing 138, 139. When the head is in its lowered position, pins 166, Fig. 1, free means connecting it to the shaft which then rotates relatively to the head for the actuation through linkage and gearing of the fingers 122.